Phenylhydrazine hydrochloride is a white to light brown or tan crystalline powder, odorless or with a slight special odor. It is the hydrochloride salt of phenylhydrazine, which has higher stability and is easier to store and transport compared with free phenylhydrazine. It is hygroscopic in air and gradually discolors when exposed to light. Its aqueous solution is acidic (pH 2.6–2.9).

1. Organic synthesis intermediate: Mainly used in the synthesis of pharmaceuticals, pesticides, dyes and pigments.

2. Analytical reagent: Used as a characteristic reagent for the identification of aldehydes, ketones and carbohydrates (forming hydrazone derivatives).

3. Biochemical research: Used in the study of proteins and enzymes as a free radical initiator.

4. Photosensitive materials: Used in the production of some special photographic chemicals.